Zn and Fe complexes containing a redox active macrocyclic biquinazoline ligand

Area of Science:

• Coordination Chemistry
• Inorganic Chemistry
• Materials Science

Background:

• Macrocyclic ligands play a crucial role in stabilizing metal complexes with unique electronic properties.
• The biquinazoline (Mabiq) ligand, featuring a bipyrimidine core and dihydropyrrole units, offers potential for novel coordination chemistry.

Purpose of the Study:

• To synthesize and characterize iron and zinc complexes coordinated by the Mabiq ligand.
• To investigate the electronic structures and redox behavior of these metal-Mabiq complexes.
• To explore the potential for radical formation and magnetic coupling within these complexes.

Main Methods:

• Synthesis of novel iron and zinc complexes with the Mabiq ligand.
• Spectroscopic characterization techniques to elucidate electronic structures.
• Density-functional theory (DFT) calculations for computational analysis.
• Isolation and characterization of iron complexes in multiple oxidation states.

Main Results:

• The zinc-Mabiq complex demonstrated ligand-centered reduction, indicating the redox non-innocence of the Mabiq ligand.
• Iron-Mabiq complexes were isolated in three distinct oxidation states: low-spin ferric, low-spin ferrous, and intermediate-spin Fe(II).
• The intermediate-spin Fe(II) complex exhibited antiferromagnetic coupling between the iron ion and a Mabiq-centered pi-radical.

Conclusions:

• The Mabiq ligand possesses significant redox activity, acting as a redox-active component in its metal complexes.
• Metal complexes of Mabiq display a rich array of electronic structures and redox states, particularly for iron.
• These findings highlight the potential of Mabiq as a versatile ligand for designing functional inorganic materials with tunable electronic and magnetic properties.